The invention relates to a liquid gas-operated lighter, particularly pocket lighter, comprising a burner tip, a fuel tank and, arranged therebetween, a non-adjustable control device for the flame height which is provided with a fuel-permeable proportioning disk of microporous film. On its side facing the fuel tank, the proportioning disk is tightly braced in its border region by means of a bracing disk which is provided with a passage for the fuel and, on its side facing the burner tip, the proportioning disk rests against a structural component having a gas-permeable layer.
In pocket lighters, particularly in those having no adjustable flame regulator, manufacturing inconsistencies lead to a great problem with respect to keeping the flame height constant, particularly with respect to achieving a uniform burning of the flame. Moreover, due to the fact that the vapor pressure of the fuel depends upon the temperature, the amount of gas discharged and, therefore, the flame height change as the temperature changes. For example, assuming a normal flame with a height of 25 mm at 25.degree. C., a temperature change of about 10.degree. C. results in a change of the flame height of about 10 mm, about 1 milligram fuel per second being consumed at a flame height of 25 mm when using, for example, isobutane gas. When the temperature influences are compounded with the manufacturing inconsistencies, unexpectedly high flames may frequently occur, which represent a safety risk.
In lighters having a wick or an ascending pipe, and in lighters in which the fuel tank contains air whose pressure is higher than the vapor pressure of the liquid gas, a decrease of the liquid level with increasing consumption also leads to a change of the flame height. Experience has shown that in known lighters even the aging in the unused state leads to a change of the originally adjusted flame characteristic. This is particularly true when the lighters are subjected to changing or extreme ambient conditions.
Also, a flickering of the flames can be frequently observed. This is particularly true for pocket lighters which are subjected to very different temperatures, on the one hand, and which are frequently in a completely undefined carrying position immediately prior to being used.
In these devices, the relative constancy of the flame height is also primarily a safety problem because unexpectedly high flames may lead to burns or to the unintentional igniting of objects. Because of the importance of this problem, even non-refillable lighters, or so-called disposable lighters, practically without exception have adjustable flame regulators, which substantially increases their manufacturing costs. Nevertheless, the problem of exceeding the permissible maximum flame height is not satisfactorily solved in this manner. Therefore, several countries are considering introducing legal limitations for such products.
A vast majority of the conventional gas lighters are provided with porous bodies serving as flow-control elements for the fuel. These flow-control elements are simultaneously used for regulating the flame height. Inasmuch as they are bodies made of fibers, the amount of fuel passing therethrough can be regulated by an appropriate compression of the body; the stronger the body is compressed, the lower becomes the amount flowing through. If the flow-control bodies consist of rigid, porous materials, such as, sintered material, the amount flowing through is regulated by covering the surface of the portions of the body exposed to the fuel by elastically deformable elements. However, it is also known to conduct the fuel through a narrow bore of a rubber-elastic element toward the burner tip and to regulate the amount flowing through by radially deforming the rubber body by applying an axial pressure, thereby reducing the diameter of the small bore serving as passage.
In these cases, the compression is adjusted during the manufacture of the lighters in such a way that the flame has a permissible height. It is left to the user to adjust a flame height deviating therefrom.
It may happen in pocket lighters that a dangerously high flame occurs at the time of ignition or during the adjustment of the flame height, which causes small droplets of liquid gas to be entrained by its gas phase, resulting in flickering of the flame. Therefore, it is desirable to limit the amount of fuel discharged. It is known that such a limitation can be achieved by a certain microporous plastics film. Such a film can be provided either instead of a flame regulating mechanism or in addition thereto, as shown by French Pat. Nos. 2,313,638 and 2,313,639. In these lighters, the porous film separates a wetting chamber from a vaporization chamber. In these lighers, it must be ensured that liquid fuel wets the membrane on the side of the film exposed to the fuel, for which purpose wicks or dip pipes are provided. As a result, the manufacture of these lighers becomes more complicated and more expensive.
It is the object of the invention to provide a simple structural design of lighters, which leads to a low reject rate in the mass production of such pocket lighters (disposable lighters). By decreasing the number of structural components, the manufacturing costs are reduced.
The invention resides in the finding, contrary to the prevailing view, that a uniform flame whose height is limited can be achieved even during long burning durations, when fuel is present in the gaseous state on the side of the membrane exposed to the fuel. However, the practical embodiment poses difficulties because the uncontrolled position of the lighter between uses always causes liquid fuel to reach the membrane and to wet the latter. Therefore, it must be ensured that the liquid fuel quickly runs off from the membrane into the tank when the lighter is positioned vertically into its position of use and that only a non-avoidable amount of liquid fuel remains in the region of the membrane. Therefore, the basic concept of the invention resides in constructing the size and shape of the structural components of the control device facing the interior of the fuel tank in such a way that as little as possible liquid fuel is retained by surface forces.
In the above-described pocket lighters having a control device, the latter has a bracing disk which tightly presses together in its border region the proportioning disk which also consists of microporous film, so that only the surface area free from compression action is available for the passage of the fuel. Such a control device meets the requirements for achieving the object of the invention if, in accordance with the invention, the bracing disk forms the conclusion of the lower end of the control device, and when, in the vertical position of use of the lighter, this end is always situated at a distance above the liquid phase of the liquid gas and the space between the control device and the level of the liquid is free from structural components.
Surprisingly, the construction of the control device in accordance with the invention results in a very uniformly burning flame and, furthermore, the lighters leaving the manufacturing plant have insignificant inconsistencies with respect to the flame height. Since the lighters have no regulating mechanism for adjusting the flame height, it is particularly important that the flame height resulting from the manufacture of the lighters is as uniform as possible and corresponds to the normal flame height of 25 mm at 298.degree. K.
An advantageous embodiment results when the surfaces and spaces of the control device and its housing facing the fuel tank and facilitating the adherence of the liquid fuel have such a size and volume that the amount of liquid fuel which adheres to these structural components due to surface forces when the lighter is moved into the normal, vertical position of use, is smaller than the amount of fuel consumed by the normal flame within three seconds, preferably within less than one second.
For improving the desired effects, the surfaces, particularly those of the bracing disk, can be provided with a coating which repels the liquid fuel.
The invention further relates to the structural design and the selection of material for the proportioning disk, bracing disk and the structural component having a gas-permeable layer. In the following, several embodiments of the invention shall be described with the aid of the drawing, without limiting the invention to these embodiments.